1. Field of the Invention
The present invention relates to a system for printing color data displayed on a color monitor of a computer, by using a color printer.
2. Related Background Art
It will be explained hereinafter a conventional technique concerning a system for printing color data on a color monitor of a computer by using a color printer.
Initially, the entire system will be briefly explained. The color data which has been edited on a host computer is stored in a memory, a filing system or the like in the host computer. In a case where the stored color data is printed by the color printer, after the color data is appropriately subjected to color correction in a gamma correction process and a matrix conversion process, obtained color information is transferred to the color printer. In the conventional technique, a color development characteristic of the monitor, a color reproduction characteristic of the color printer, and the like can be predicted or foreseen within a range of restricted accuracy or precision. For example, measurement of a sample which is performed by measurement equipment or the like and a model which is obtained by using interpolation calculation are defined to be applied to such prediction.
In such system, for example, color matching between a color on the color monitor and a color on the color printer can be realized by appropriately adjusting parameters applied to the above-described gamma correction process and the matrix conversion process. In many cases, such parameter is determined by a simulation calculation such as a least square or the like. At that time, there is a merit function (or performance function) or the sample as a factor which significantly affects a result of such determination. Ordinarily, a color space which is perceptibly uniform is defined, and a distance (i.e., color difference or chrominance) in such color space is used as the performance function. Further, as the sample, samples are ordinarily used which are appropriately diffusive.
However, even in a color matching system which has been theoretically designed, there is a remarkable difference between the color on the color monitor and the color on the color printer. That is, the color difference itself in the above-described uniform color space has been applied on the premise of the color matching between the same media (e.g., printed matter versus printed matter). Therefore, if the color difference is used, the color matching between different-kinds of media (e.g., monitor versus printed matter) does not always succeed.
In such case, the most serious problem occurs when a displacement or an aberration occurs in hue.
In order to clarify such problem as to the displacement in hue, the perceptible same hue (i.e., same hue in sight) should be strictly separated from the same hue consisting of each primary color in a device in a monitoring system (e.g., EBU (European Broadcasting Union) system, NTSC (National Television System Committee) system or the like).
In the perceptible same hue, the same hue is defined by human sight or view as being representative of the Munsell color system. Generally, the so-called uniform color space is correctly named as a perceptible uniform color space. Ideally, such perceptible uniform color gamut is designed such that the perceptible same hue is linearly mapped from an origin. On the other hand, the same hue in an RGB (red, green and blue) device is defined as the same hue for a color group in which a ratio of each input value is constant. For example, in a case where each of R, G and B is represented as (R, G, B) with values 0 to 255, it is assumed that blue groups (0, 0, 0)xe2x86x92(0, 0, 64)xe2x86x92(0, 0, 128)xe2x86x92(0, 0, 192)xe2x86x92(0, 0, 225) on the monitor have the same hue.
In a case where each color on the monitor is mapped to the perceptible uniform color space, each color is linearly mapped. Therefore, the same-hue color in the monitor system tends to be considered as having the same hue in the uniform color space. However, when the color on such a line is actually reproduced by the color printer, blue (0, 0, 255) in a primary color is printed as purple, whereby the printed blue is viewed as a color remarkably different from the blue on the monitor.
In a case where the uniform color space is a coordinate space in which the same hue defined in sight is linearly mapped, and in a case where the same-hue color on the monitor is plotted in the uniform color space, although such same hue is linearly represented, the color on a monitor is viewed as the different-hue color on the printer. It is supposed that this is complicatedly affected by a difference between a color area of the Munsell color system and a color area of the monitor, a relation between hue and saturation and the like. Therefore, even if some correction is not performed, such problem can not be solved.
An object of the present invention is to provide an image processing apparatus and method which can faithfully reproduce a color in a displayed image.
In order to achieve the above object, there is provided in the present invention an image processing method of generating a color image by using a color palette table, comprising the steps of:
restricting colors which can be registered in the palette table, on the basis of gamut data of an image output means outputting the color image;
forming the color palette table on the basis of the color restriction obtained in the restriction step; and
generating the color image by using the colors which have been registered in the color palette table.
Another object of the present invention is to provide an image processing apparatus and method which absorb a system difference between color development and light generation, a difference in media or the like, and performs matching in color appearance between a color in a generated image and color in the displayed image.
In order to achieve the above object, there is provided in the present invention an image processing method comprising:
an input step of causing an image formation means to form a target image on the basis of target data, and inputting image data obtained by reading the target image with an image read means;
correction step of correcting the target data belonging to a range neighboring a predetermined hue such that its saturation is raised and its hue is rotated, so as to generate the corrected target data; and
a color process parameter generation step of generating a color process parameter on the basis of the image data and the corrected target data.
The above and other objects of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings.